Who makes quality sealed box speakers?

Very few. But if you want a very good used one The Avalon Radian and Radian HC are your ticket. In fact I prefer my Radian model to the older Eidolon model ( which is a modified port design), particularly the integration of the bass to the midrange.... very seductive!

Any even better question is:

Who makes a sealed active speaker?

Well, Vandersteen for one. The 2ce sig, 3a sig and 5a's are all sealed designs. The 1c is a tuned transmission line.